Frequency modulated electric oscillators utilizing variable capacitance semiconductor diodes



March 26, 1968 D DAWSON 3, 5, 9

FREQUENCY MODULATED ELECT RIC OSCILLATORS UTILIZING VARIABLE CAPACITANCESEMICONDUCTOR DIODES Filed NOV. 8, 1966 24 20 I 18 Modulation PowerSource Supply IN EH bR Dru/m Dqwfov BY 6.444; 64 ziw/ 0/43 United StatesRttetrt Cfilice 3,375,469

Patented Mar. 26, 1968 3 375 469 A variable frequency electricoscillator in accordance v with the present invention will now bedescribed by way of example with reference to the accompanying drawing,SEMICONDUCTOR DIODES which shows the oscillator diagrammatically.

D i Dawson, Coventry, l assignor The 5 The oscillator comprises an n-p-n junction transistor 1, eral Electric Company Limited, London,England, a the emitter electrode of which is connected by way of aBritish company NSISIOI 2 I0 a negative supply 11116 3 by way Ol El62136101- ill 3 In the example quoted above component values were asfollows:

Resistor 2 ohms 620 Resistor 6 kilohmS 3.9 Resistor 7 do 12 Resistor 10ohms 620 Capacitor 4- picofarads 47 Capacitor 5 do 22 Capacitor8 do 1000Capacitor 13 do 1000 Inductor 12 microhenrys 0.8 Transistor 1 type(Ferranti) ZT 2708 Diode 11 type (Fijitsu) IS 518 I claim:

1. A frequency modulated electric oscillator comprising a transistor, aseries tuned circuit comprising in order, a variable capacitancesemiconductor diode, an inductor and a capacitor of large value comparedwith the value of capacitance of the variable capacitance diode, powersupply means, means connecting said series tuned circuit between thecollector electrode of said transistor and one pole of said power supplymeans such that said collector electrode is connected to one terminal ofsaid variable capacitance diode, means connecting said transistor to theother pole of said power supply means for energization of thetransistor, capacitive feedback means connected between the collectorand emitter electrodes of said transistor, means to apply asubstantially constant voltage across said capacitor of large value, amodulation source, and means to apply a frequency modulating signalvoltage from said source to the junction between the collector electrodeof said transistor and said variable capacitance diode.

2. A frequency modulated electric oscillator in ac cordance with claim 1wherein the means to apply the frequency modulating signal voltage fromthe source comprises a further transistor of opposite conductivity typeto the first mentioned transistor, and means connecting said furthertransistor for energization from said power supply means as a bufferamplifier, said last mentioned means including a connection between theemitter electrode of said further transistor and the junction betweenthe C01- lector electrode of the first mentioned transistor and thevariable capacitance diode.

References Cited UNITED STATES PATENTS 2,984,794 5/1961 Carter et al.331-117 3,249,897 5/1966 Trilling. 3,302,138 1/1967 Brown et al 331--116 OTHER REFERENCES Electronic Industries, August 1965, p. 168.

JOHN KOMINSKI, Primary Examiner.

